A confocal scanning microscope has a laser module which preferably includes a plurality of laser beam sources to generate illumination light with different wavelengths. The illumination light forms an illumination beam that is coupled into a scanning device. The scanning device includes a main color splitter, an xy-scanner, a scanning lens, and a microscope lens.
The scanning device guides the illumination beam via the scanning lens and the microscope lens to a sample that is placed on a microscope stage of the confocal scanning microscope. A measurement light beam that originates from the sample is directed via the main color splitter and a projection lens onto at least one confocal detection stop (detection pinhole) of at least one detection channel.
An image of the sample may be recorded by photomultiplier tubes or photomultipliers (PMTs) and amplifiers may be arranged downstream of the PMTs. The amplifiers have a predefined constant bandwidth. The effective bandwidth of the PMTs depends on the scanning speed. Therefore, the scanning speed is set to a maximum scanning speed which results in a large bandwidth.
For low scanning speeds, however, a large bandwidth is not required and has even a negative impact on the signal-to-noise ratio (SNR), and hence on the image quality, since more noise is recorded.